The purpose of this project is to determine which immune indices, measured predominantly by in vitro assays, correlate best with in situ immune function, and to miniaturize these assays. The topics presented include (1) optimal culture conditions for PHA response, (2) comparative studies on human spleen, lymph nodes, and peripheral blood, (3) comparative studies between immunologic parameters of human and mouse lymph nodes and spleen, and (4) studies on peripheral blood and splenic cells from patients with hairy cell leukemia. BIBLIOGRAPHIC REFERENCES: Kay, M.M.B.: Autoimmune disease: the consequence of deficient T cell function? J. Amer. Geriat. Soc. 24: 253-257, 1976. Kay, M.M.B.: High Resolution Scanning Electron Microscopy and its Application to Research on Immunity and Aging. In Makinodan, T. and Yunis, E. (Eds.): Immunology and Aging. New York, Plenum Medical Book Co., 1977, pp. 135-150.